Investigating the Effect of Functional Group on Folic Acid Conjugation and <i>in vitro</i> Characteristics of Lomustine from Silica Nanoparticles

Herein, silica nanoparticles (SNs) with different functional groups (propyl amine, propyl thiol, propyl carboxylic acid and unmodified hydroxyl) were loaded with the anticancer agent lomustine (LMS) and conjugated with Folic Acid (FA) to produce FA-NH2-SNs, FA-SH-SNs, FA-COOH-SNs, and FA-OH-SNs, respectively. The nanoparticles (NPs) were characterized using Fourier Transform Infrared Spectroscopy (FTIR) and Dynamic Light Scattering (DLS). Encapsulation Efficiency (EE) and drug release rate were measured using UV Spectrophotometer. The in vitro cytotoxicity toward HeLa and VERO cells was assessed using MTT assay. LMS encapsulation efficiency exceeded 40% and FTIR spectra confirmed a successful conjugation with FA. Particle size increased after LMS loading and FA conjugation, ranging from 284 to 308 nm. Zeta potential measurements showed that all NPs became more negative after FA conjugation. The largest shift occurred in NH2-SNs, changing from about - 4 to -14 mV. One-way ANOVA showed statistically significant differences (p < 0.05) among most formulations for drug release rates and cytotoxicity which were lower compared to free drug. The cytotoxicity was higher against HeLa compared to VERO cells due to folate-receptor targeting. The order of cell toxicity effect was almost related to their release rate behaviors where FA-NH2-SNs exhibited the lowest percentages (18% and 40%, respectively). Thus, the type of surface functional group significantly influenced the efficiency of FA conjugation, which in turn modulated the in vitro characteristics of the loaded drug where higher conjugation correlated with reduced release rates and cytotoxicity.